Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-06-18
2001-11-20
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S060000, C606S064000, C606S062000, C606S063000, C606S067000, C606S068000, C606S075000, C623S016110, C623S020360
Reexamination Certificate
active
06319255
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a prophylactic implant against fractures of osteoporosis-affected bone segments.
There are millions of osteoporotic persons in Germany alone, who most frequently have other diseases of the locomotor system.
Osteoporosis is accompanied by a loss of the bone mass, which exceeds the natural age-related bone disintegration. In addition, the quality of the microstructure of the bone tissue degrades. The loss of the bone mass, bone structure and function leads to clinical symptoms with lasting infirmities and fractures. Femoral neck fractures, fractures of the vertebral column and of the wrist are particularly widespread.
In the case of osteoporotic fractures of the femoral neck, the treatment at the present time mainly involves the complete resection of the femur and natural acetabulum, as well as the implantation of a complete artificial hip joint system. These systems are presently quite well developed, but this intervention should nevertheless be regarded as a severe intervention as has always been the case. In addition, as before, particularly critical is the long-term stability of the implant in the patient body. Influences on this have been, for example, the type of implant (with or without cementing), age and constitution of the patient, as well as many other parameters. Apart from this, it would be desirable if the total resection of bone segments could be deferred as long as possible, even in osteoporotic patients, or would become completely superfluous.
Starting points for an early diagnosis of the anticipated trauma or the fracture of the affected bone segment follow from modern radiological examinations. Signs of the osteoporosis-induced alterations in the bone structure can be clearly determined radiologically, and interestingly, the anticipated fracture can be predicted with astonishingly high accuracy within a period up to one year. This knowledge gives the opportunity and the chance to intervene therapeutically before the fracture occurs and to stop or retard the osteoporosis.
An implant, which can also be used for prophylactic purposes, is known from U.S. Pat. No. 2,537,070. The implant has a thin-walled reinforcing body with a plurality of passages in its outer wall. Pulverized bone material is pressed into the reinforcing body during the implantation. A contact between the spongiosa surrounding the implant and the pulverized bone material is allowed by the openings in the wall of the implant. A fixation should be achieved thereby through absorption of moisture through the surrounding bone structure.
From German published patent application DE-A-195 08 224 an implant is known which can be inserted as a prophylactic implant against fractures of osteoporosis-affected bone segments. This implant consists of a solid implant core forming a reinforcing core for the bone segment. The surface of the core member is coated with a surface layer of a dense or porous biocompatible material. The described implants are thought, in the first place, to repair defects which have already occurred, i.e., osteoporotic bones threatened by a fracture can possibly be protected beforehand. The above-mentioned early diagnosis of an anticipated trauma or the fracture still plays no role for the known implants.
SUMMARY OF THE INVENTION
In view of this background, it is an object of the present invention to provide an implant against fractures of osteoporosis-affected bone segments, which in a particular manner is suited for a prophylactic use.
According to the first embodiment, the prophylactic implant has a thin-walled hollow reinforcing body with such a large number of passages in its outer wall, that the ratio of the total area of the passages (i.e., the area of the openings of the passages on the outer wall) to the total surface area (i.e., the area of the outer wall including openings therein) is at least 1:2.
The reinforcing body can in the broadest sense also be designated as a reinforcing sleeve. It is essential that its interior allow the possibility of the bone material growing through the passages into its interior, or in another embodiment, bioresorbable material in the interior of the reinforcing body is gradually resorbed and replaced by bone material growing in from outside. The reinforcing body according to the invention thereby forms a place holder or seat for after-growing sound bone material, in place of the previously-removed osteoporotic bone material.
As far as the operation is concerned, the osteoporosis-affected bone segment is milled out or drilled out, and a reinforcing body according to the invention, form-fitted to the resulting bore, is inserted into the bone segment being treated. The thus treated bone segment is then closed up again in a conventional manner. This operation provides a reinforcing body, which is initially hollow, to remain in the interior of the bone segment being treated. On account of the local conditions and in case of a rough surface of the reinforcing body, the bone material grows from outside into the interior of the reinforcing body and, indeed, until the body is completely filled with natural spongiosa. This spongiosa no longer has to adhere to the defective osteoporosis-affected bone material; the structure and the stability of the affected bone are thereby again produced.
Alternatively, the operating surgeon can proceed by filling the interior of the reinforcing body with a healing enhancement agent, wherein here particularly a hydroxylapatite or an alpha-tricalcium phosphate ceramic is intended. This material can optionally be pressed into the interior of the reinforcing body as a plug by means of an appropriate tool. The material is bioresorbable, so that after a resorption of the material in the course of time, the natural bone material grows into the interior of the reinforcing body.
In addition to the main effect, that an osteoporosis-induced fracture of the bone segment can be delayed or completely avoided, it is also to be cited that the burden on the patient during the operation is substantially reduced in comparison with that of the implantation of a complete replacement implant, since the prophylactic implant according to the invention can be implanted in the course of an ambulatory intervention with only a local anesthesia. If the prophylactic implant according to the invention is thus put in place within the forecast time frame of up to one year before a fracture of the affected bone segment occurs, there is a high probability of a decided unburdening of the patient from the otherwise total operative intervention becoming necessary, since the joint itself is generally still intact at the time of the precautionary examination.
According to a first preferred embodiment, the reinforcing body is made of a biocompatible metal, and it is provided with an open-mesh, three-dimensional spatial network structure on sections of its surface. The above-mentioned spatial network structure serves to allow the surrounding bone material to grow through this structure and thus exercises a restraining effect against movement of the implant from the milled out bore in the bone segment being treated. In the extreme case, i.e., with a very large ratio of the total area of the passages to the total surface area, the reinforcing body can be a sort of metal network. The three-dimensional spatial network structure can then be provided, depending on the place of implantation, at chosen points of the surface of the implant.
According to another preferred embodiment, it is provided that the reinforcing body is made of a biocompatible dimensionally stable, yet still elastic, plastic, wherein the reinforcing body is deformable by means of a built-in mechanism by application of a pulling force (tension). The deformation of the reinforcing body, which is imparted as required, has the purpose of holding it in place, i.e., to prevent a displacement from the zone of implantation. The deformation is possible since the implant body is made of an elastic plastic in this embodiment described above.
In a special
Grundei Hans
Thomas Wolfram
Akin Gump Strauss Hauer & Feld L.L.P.
ESKA Implants GmbH & Co.
Reip David O.
LandOfFree
Prophylactic implant against fracture of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Prophylactic implant against fracture of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Prophylactic implant against fracture of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587660